U.S. patent number 6,806,118 [Application Number 10/347,224] was granted by the patent office on 2004-10-19 for electrode connection method, electrode surface activation apparatus, electrode connection apparatus, connection method of electronic components and connected structure.
This patent grant is currently assigned to Fujitsu Limited. Invention is credited to Masataka Mizukoshi, Keishiro Okamoto, Yasuo Yamagishi.
United States Patent |
6,806,118 |
Okamoto , et al. |
October 19, 2004 |
Electrode connection method, electrode surface activation
apparatus, electrode connection apparatus, connection method of
electronic components and connected structure
Abstract
An electrode connecting method of connecting a first electrode
and a second electrode is disclosed. The respective bonding
surfaces of the first and second electrodes are activated. Then,
each of the first and second electrodes having the activated
surfaces is coated with a coating member for maintaining an
activated state. A solid state bond between the first electrode and
the second electrode is formed by pressure welding the first
electrode and the second electrode so that the first and second
electrodes break through the coating members.
Inventors: |
Okamoto; Keishiro (Kawasaki,
JP), Mizukoshi; Masataka (Kawasaki, JP),
Yamagishi; Yasuo (Kawasaki, JP) |
Assignee: |
Fujitsu Limited (Kawasaki,
JP)
|
Family
ID: |
27667510 |
Appl.
No.: |
10/347,224 |
Filed: |
January 21, 2003 |
Foreign Application Priority Data
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Feb 7, 2002 [JP] |
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2002-031025 |
Feb 7, 2002 [JP] |
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2002-031089 |
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Current U.S.
Class: |
438/108;
257/E21.503; 438/110 |
Current CPC
Class: |
H01L
21/563 (20130101); H01L 24/29 (20130101); H05K
3/328 (20130101); H01L 2224/73203 (20130101); H01L
2224/73104 (20130101); H01L 2224/13111 (20130101); H01L
2224/13109 (20130101); H01L 2224/29111 (20130101); H01L
2224/29109 (20130101); H01L 2924/1579 (20130101); H01L
2224/2919 (20130101); H01L 2924/0133 (20130101); H01L
2924/0132 (20130101); H01L 2924/01033 (20130101); H01L
2924/01006 (20130101); H05K 3/3489 (20130101); H01L
2924/3511 (20130101); H01L 2924/01082 (20130101); H01L
2924/01078 (20130101); H01L 2924/0105 (20130101); H01L
2924/01049 (20130101); H01L 2924/01047 (20130101); H01L
2924/01029 (20130101); H01L 2924/01018 (20130101); H01L
2924/01005 (20130101); H01L 2224/83193 (20130101); H01L
2224/83101 (20130101); H01L 2924/0133 (20130101); H01L
2924/01029 (20130101); H01L 2924/01047 (20130101); H01L
2924/0105 (20130101); H01L 2924/0132 (20130101); H01L
2924/01047 (20130101); H01L 2924/0105 (20130101); H01L
2924/0132 (20130101); H01L 2924/01049 (20130101); H01L
2924/0105 (20130101); H01L 2924/0132 (20130101); H01L
2924/0105 (20130101); H01L 2924/01082 (20130101); H01L
2924/0132 (20130101); H01L 2924/0105 (20130101); H01L
2924/01083 (20130101); H01L 2224/13111 (20130101); H01L
2924/01047 (20130101); H01L 2924/00014 (20130101); H01L
2224/13111 (20130101); H01L 2924/01083 (20130101); H01L
2924/00014 (20130101); H01L 2224/13111 (20130101); H01L
2924/01029 (20130101); H01L 2924/01047 (20130101); H01L
2924/00014 (20130101); H01L 2224/13111 (20130101); H01L
2924/01082 (20130101); H01L 2924/00014 (20130101); H01L
2224/13109 (20130101); H01L 2924/0105 (20130101); H01L
2924/00014 (20130101); H01L 2224/2919 (20130101); H01L
2924/0665 (20130101) |
Current International
Class: |
H01L
21/02 (20060101); H01L 21/56 (20060101); H05K
3/32 (20060101); H05K 3/34 (20060101); H01L
021/44 (); H01L 021/48 (); H01L 021/50 () |
Field of
Search: |
;438/108,109,110,615 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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11-87561 |
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Mar 1999 |
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JP |
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11-274224 |
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Oct 1999 |
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JP |
|
Primary Examiner: Fourson; George
Assistant Examiner: Toledo; Fernando L.
Attorney, Agent or Firm: Armstrong, Kratz, Quintos, Hanson
& Brooks, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority
from the prior Japanese Patent Applications No. 2002-031089 filed
on Feb. 7, 2002 and No. 2002-031025 filed on Feb. 7, 2002, the
entire contents of which are incorporated herein by reference.
Claims
What is claimed is:
1. An electrode connecting method of connecting a first electrode
and a second electrode, comprising the steps of: (a) activating
respective bonding surfaces of the first and second electrodes; (b)
coating each of the first and second electrodes having the
activated bonding surfaces with a coating member for maintaining an
activated state; and (c) forming a solid state bond between the
first and second electrodes by pressure welding the first and
second electrodes so that the first and second electrodes break
through the coating members.
2. The electrode connecting method as claimed in claim 1, wherein
when activating respective bonding surfaces of the first and second
electrodes, the activation is performed by eliminating oxide films
formed on the bonding surfaces.
3. The electrode connecting method as claimed in claim 1, wherein
etching by irradiating plasma is used as the activation process for
activating the respective bonding surfaces of the first and second
electrodes.
4. An electrode connecting method of connecting a first electrode
and a second electrode, comprising the steps of: (a) activating
respective bonding surfaces of the first and second electrode; (b)
coating each of the first and second electrodes having the
activated bonding surfaces with a coating member for maintaining an
activated state; and (c) forming a solid state bond between the
first and second electrodes by pressure welding the first and
second electrodes so that the first and second electrodes break
through the coating members, wherein reduction of a formic acid is
used as the activation process of activating the respective bonding
surfaces of the first and second electrodes.
5. The electrode connecting method as claimed in claim 1, wherein
an adhesive film having an electrical insulation property is used
as the coating member for maintaining the activated state.
6. The electrode connecting method as claimed in claim 1, wherein
the step (b) is performed in an inert gas atmosphere.
7. The electrode connecting method as claimed in claim 1, wherein
the first and second electrodes are protruding electrodes formed on
respective boards.
8. A method of directly connecting components via respective
electrodes, each component having an electrode and at least one of
the components being an electronic component, comprising the steps
of: (a) applying a metal material having Young's modulus of equal
to or less than 50 GPa to a surface of the electrode of at least
one of the components; (b) activating a surface of the metal
material and a surface of the electrode of another component when
the metal material is not applied to the surface of the electrode
of the other component; (c) coating each of the electrodes having
the activated bonding surfaces with a coating member for
maintaining an activated state; and (d) connecting the components
by forming a solid state bond between the respective electrodes of
the components via the applied metal material by pressure welding
the electrodes so that the electrodes break through the
coating.
9. The method as claimed in claim 8, wherein the metal material
applied to the surface of the electrode is selected from among a
Sn, a Sn--Ag alloy, a Sn--Bi alloy, a Sn--Ag--Cu alloy, a Sn--In
alloy and a Sn--Pb alloy.
10. The method as claimed in claim 8, wherein the metal material
applied to the surface of the electrode has a thickness equal to or
less than 5 .mu.m.
11. The method as claimed in claim 8, wherein the metal material is
applied by one of a dipping method, an ultrasonic soldering method,
and a transfer method.
12. A method of directly connecting components via respective
electrodes, each component having an electrode and at least one of
the components being an electronic component, comprising the steps
of: (a) applying a metal material having Young's modulus of equal
to or less than 50 GPa to a surface of the electrode of at least
one of the components; (b) activating a surface of the metal
material and a surface of the electrode of another component when
the metal material is not applied to the surface of the electrode
of the other component; and (c) connecting the components by
forming a solid state bond between the respective electrodes of the
components via the applied metal material, wherein the step (b) is
performed by one of irradiating plasma and exposing to a heated
carboxylic acid atmosphere.
13. The method as claimed in claim 8, wherein one of the components
is a semiconductor chip and the other of the components is either a
board mounting the semiconductor chip or another semiconductor
chip.
14. A connected structure in which components are directly
connected via respective electrodes and a metal material for
bonding arranged between the electrodes, wherein the components are
connected by a method comprising the steps of: (a) applying a metal
material having Young's modulus of equal to or less than 50 GPa to
a surface of the electrode of at least one of the components; (b)
activating a surface of the metal material and a surface of the
electrode of another component when the metal material is not
applied to the surface of the electrode of the other component; (c)
coating each of the electrodes having the activated bonding
surfaces with a coating member for maintaining an activated state;
and (d) connecting the components by forming a solid state bond
between the respective electrodes of the components via the applied
metal material by pressure welding the electrodes so that the
electrodes break through the coating.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrode connection methods,
electrode surface activation apparatuses, electrode connection
apparatuses, connection methods of electronic components, and more
particularly to an electrode connection method, an electrode
surface activation apparatus and an electrode connection apparatus
that connect electrodes by solid state bonding, a method of
directly connecting components to be connected via the respective
electrodes, and a connected structure including electrical
components connected by the method.
2. Description of the Related Art
The demand for high density mounting of electronic components is
increasing based on smaller and thinner electronic equipment of
these years. Thus, when connecting an electronic component such as
a semiconductor chip to a board, a mounting method of flip chip
bonding a bare chip provided with protruding electrodes (bumps) to
a board is often employed. Protruding electrodes are formed on a
semiconductor chip used for flip chip bonding, and it is necessary
to electrically connect the protruding electrodes to the wiring on
the board.
The major example of protruding electrodes of an electronic
component is solder bumps. There is the reflow soldering method as
a method of connecting the electronic component to the circuit
board in a case where the solder bumps are used. In the reflow
soldering method, flux for eliminating an oxide film on the solder
is applied to the electrodes on a board so as to improve the solder
bonding. Then, the electronic component is positioned and mounted
on the board. Thereafter, the electronic component and the board
are electrically connected by the reflow such that the solder bumps
are melted in a furnace having an air atmosphere or a nitrogen
atmosphere so as to wet the electrodes of the board with the melted
solder and spread the solder on the electrodes. Generally, the
electronic component and the circuit board are mechanically
connected by filling and curing a resin for sealing between the
electronic component and the circuit board. The reflow soldering
method is also employed when forming a stacked structure by
stacking electronic components.
Recently, solid state bonding has been attracting attention as a
method of mounting a highly integrated smaller semiconductor device
to a board at low temperature and low pressure with high
reliability and low damage. As a specific connection method of
solid state bonding, a method is known where bonding surfaces of
electrodes (for example, the electrodes of a semiconductor device
and the electrodes of a board to which electrodes the electrodes of
the semiconductor are connected) are placed in direct contact with
each other and pressed so as to form a solid state bond. More
specifically, a method is known where a firm bond (solid state
bond) is formed between metal atoms at room temperature, after
activating the surface of the metal forming the electrodes by
eliminating an oxide film existing on the surfaces of the
electrodes.
However, when a pollutant or an oxide film such as an oxide exists
on the bonding surfaces, it is impossible to form a firm solid
state bond of metal atoms. Accordingly, when forming the solid
state bond, the elimination of the oxide film and activation are
performed on the bonding surfaces.
As specific methods of eliminating the oxide film of the bonding
surfaces so as to activate the bonding surfaces, there are a method
of irradiating an inert gas ion beam or an inert gas high-speed
atom beam on the bonding surfaces, a method of applying ultrasonic
waves to the bonding surfaces, a method of applying friction to the
bonding surfaces, and so on.
In addition, after activating the electrodes by the above-described
methods, until the electrodes are connected to each other, it is
necessary to maintain the state where the surfaces of the
electrodes are activated. This is because even if the elimination
of the oxide film of the bonding surfaces and the activation
process of the bonding surfaces are performed, when the bonding
surfaces are returned (exposed) to the air, the oxide film is
formed on the bonding surfaces again.
Therefore, conventionally, when the elimination of the oxide film
and the activation process end, the activated electrodes are
maintained in a vacuum or an inert gas atmosphere. Further, the
connecting process of the electrodes is performed in the same
atmosphere.
However, when the above-described conventional methods are
employed, until the solid state bond is formed after the activation
of the electrode surfaces, it is necessary to maintain the state
where the electrodes are activated. For this reason, a mechanism is
required for maintaining the electrode surfaces in the vacuum or
the inert gas atmosphere.
Accordingly, it is impossible to use a flip chip bonder capable of
connecting the components in the air and having a high mounting
speed. Thus, there has been a problem in that the efficiency of the
connecting process of the electrodes is degraded. In addition, in
order to make the connecting process more efficient, when the
mechanism for realizing the inactive gas atmosphere is provided to
the flip chip bonder, the equipment becomes complex and expensive.
Thus, the equipment cost increases.
In addition, in the above-described reflow soldering by the solder
bumps, since the melting point of the solder is generally high such
as equal to or more than 200.degree. C., there is a possibility of
the electronic component being thermally damaged. Moreover, shorts
tend to occur between the adjacent electrodes when the solder
melted in the reflow flows out from the electrode areas. Further,
since the thermal expansion coefficient of the electronic component
and the thermal expansion coefficient of the circuit board are
different, shearing stress and strain are applied to the bonded
parts connected by the reflow solder. Accordingly, the reliability
of the connection is likely to be reduced.
On the other hand, in the method of forming the solid state bond
such that the bonding surfaces are in direct contact with and
pressed against each other after cleaning and activating the
electrode surfaces of the components to be connected, it is
difficult to achieve firm connection. The reason is that, since
irregularities on the order of submicrons or microns originally
exist on the electrode surfaces, the planarization of the electrode
surfaces is difficult to achieve even if the electrode surfaces are
cleaned, and thus the effective contact area of the electrodes is
small. When the force on the connection is increased so as to
improve the connection strength, the electronic component may be
damaged. Additionally, when a polarization process such as the
chemical-mechanical polishing (CMP) is performed so as to eliminate
the irregularities on the electrode surfaces, problems such as an
increase in the manufacturing cost and an increase in the TAT (turn
around time) arise.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an
improved and useful electrode connection method, electrode surface
activation apparatus, electrode connection apparatus, and
connection method of electronic components in which the
above-mentioned problems are eliminated.
It is another and more specific object of the present invention to
provide an electrode connecting method, electrode surface
activation apparatus, and electrode connecting apparatus that can
simply and inexpensively form a solid state bond between
electrodes.
It is still another object of the present invention to provide a
method enabling the connection between an electronic component and
a mounting board such as a circuit board or between electronic
components with high reliability at low temperature and low load in
which the above-described problems in the prior art are
eliminated.
In order to achieve the above-mentioned objects, according to one
aspect of the present invention, there is provided an electrode
connecting method of connecting a first electrode and a second
electrode, including the steps of: (a) activating respective
bonding surfaces of the first and second electrodes; (b) coating
each of the first and second electrodes having the activated
surfaces with a coating member for maintaining the activated state;
and (c) forming a solid state bond between the first and second
electrodes by pressure welding the first and second electrodes so
that the first and second electrodes break through the coating
members.
According to the above-mentioned aspect of the present invention,
the bonding surfaces are sealed (coated) with the coating member
after performing the activation process on the bonding surfaces of
the first and second electrodes. Thus, it is possible to maintain
the state where the bonding surfaces are activated even when the
first and second electrodes are placed (exposed) in the air.
In addition, when forming the solid state bond between the
respective bonding surfaces of the first and second electrodes,
each of the electrodes breaks through the coating member so as to
form the solid state bond. Therefore, it is possible to form the
solid state bond in the air. Hence, it is possible to correspond to
the mass production process since the connecting in the air
according to the flip chip method can be applied.
Additionally, according to another aspect of the present invention,
in the above-described electrode connecting method, the activation
may be performed by eliminating the oxide formed on the bonding
surfaces, when activating the respective bonding surfaces of the
first and second electrodes.
According to the above-mentioned aspect of the present invention,
it is possible to connect the electrodes while maintaining the
state where the surfaces of the electrodes of electronic components
are activated by eliminating the oxide formed on the surfaces of
the electrodes. For this reason, it is possible to achieve the
improvement in the yield of the connecting process since the solid
state bond having high reliability can be achieved with low
temperature and low load.
In addition, according to another aspect of the present invention,
in the above-described electrode connecting method, etching by
irradiating plasma may be used as the activation process of
activating the respective bonding surfaces of the first and second
electrodes.
According to the above-mentioned aspect of the present invention,
the bonding surfaces are activated by the plasma etching. Thus, it
is possible to positively activate a plurality of electrodes at a
high throughput.
Further, according to another aspect of the present invention, in
the electrode connecting method, the reduction of a formic acid may
be used as the activation process of activating the respective
bonding surfaces of the first and second electrodes.
According to the above-mentioned aspect of the present invention,
the bonding surfaces are activated by using the reduction of the
formic acid. Hence, it is possible to surely activate the plurality
of electrodes with inexpensive equipment.
Additionally, according to another aspect of the present invention,
in the electrode connecting method, an adhesive film having an
electrical insulation property may be used as the coating member
for maintaining the activated state.
According to the above-mentioned aspect of the present invention,
it is possible to easily perform the coating process for
maintaining the activated state of the electrodes by using, as the
coating member, an adhesive film having an electrical insulation
property. In addition, it is possible to correspond to the
automation of the coating process of the electrodes with ease.
Furthermore, according to another aspect of the present invention,
in the electrode connecting method, the coating process of coating
the first and second electrodes with the coating member may be
performed in an inert gas atmosphere.
According to the above-mentioned aspect of the present invention,
it is possible to maintain the activated state of the electrodes
more positively, since the air causing the oxidization of the
electrodes does not exist in between each of the electrodes and the
coating member.
Additionally, according to another aspect of the present invention,
in the electrode connecting method, the first and second electrodes
may be protruding electrodes formed on the respective boards.
According to the above-mentioned aspect of the present invention,
since the first and second electrodes are the protruding
electrodes, when forming the solid state bond between the first and
second electrodes by breaking through the coating member by the
first and second electrodes, it is possible to positively perform
the process of breaking through the coating member. Thus, it is
possible to prevent the coating member from remaining in between
the electrodes.
In addition, according to another aspect of the present invention,
there is provided an electrode surface activation apparatus
activating surfaces of electrodes, including: a first apparatus
activating bonding surfaces of the electrodes; and a second
apparatus coating the electrodes of which bonding surfaces are
activated with a coating member for maintaining an activated
state.
According to the above-mentioned aspect of the present invention,
the bonding surfaces of the electrodes are activated by the first
apparatus, and the activated electrodes are coated with the coating
member by the second apparatus. Hence, it is possible to perform
the process of applying the coating member to the electrodes with a
simple construction.
In addition, according to another aspect of the present invention,
in the above-described electrode surface activation apparatus, the
first apparatus may activate the bonding surfaces of the electrodes
by eliminating the oxide film formed on the bonding surfaces.
Further, according to another aspect of the present invention, in
the above-described electrode surface activation apparatus, the
first apparatus may etch the bonding surfaces by irradiating plasma
so as to activate the bonding surfaces.
Additionally, according to another aspect of the present invention,
in the electrode surface activation apparatus, the first apparatus
may activate the bonding surfaces by using the reduction of formic
acid.
Furthermore, according to another aspect of the present invention,
in the electrode surface activation apparatus, an adhesive film
having an electrical insulation property may be used as the coating
member for maintaining the activated state.
In addition, according to another aspect of the present invention,
in the electrode surface activation apparatus, the second apparatus
may perform the process of coating the electrode with the coating
member in an inert gas atmosphere.
Further, according to another aspect of the present invention,
there is provided an electrode connecting apparatus, including an
electrode surface activation apparatus and a bonding apparatus, the
electrode surface activation apparatus including: a first apparatus
activating bonding surfaces of the electrodes by eliminating an
oxide on the bonding surfaces; and a second apparatus coating the
electrodes with a coating member for maintaining an activated
state, the electrodes having activated bonding surfaces, the
bonding apparatus forming a solid state bond between a pair of
electrodes by pressure welding the pair of electrodes so that the
electrodes break through the coating member, the pair of electrodes
having bonding surfaces activated by the electrode surface
activation apparatus.
As mentioned above, according to the present invention, the bonding
surfaces of the electrodes are activated by the electrode surface
activation apparatus, the activated state of the electrodes are
maintained by the coating member, and the electrodes are connected
by the bonding apparatus. Accordingly, it is possible to form the
solid state bond having high reliability in the bonding with low
temperature and low load. At the same time, it is possible to
correspond to the mass production processes, and thus the
production cost can be reduced drastically.
Furthermore, according to another aspect of the present invention,
there is provided a method of directly connecting components via
respective electrodes, each components having an electrode and at
least one of the components being an electronic component,
including the steps of: (a) applying a metal material having a
Young's modulus equal to or less than 50 GPa to a surface of the
electrode of at least one of the components; (b) activating a
surface of the metal material and a surface of the electrode of the
other component when the metal material is not applied to the
surface of the electrode thereof; and (c) connecting the components
by forming a solid state bond between the respective electrodes of
the components via the applied metal material.
According to the above-mentioned aspect of the present invention,
the respective electrodes of the components are connected while
maintaining a state where the oxide on the electrode surface of the
component and the oxide on the surface of the metal material for
bonding are eliminated and activated. Thus, it is possible to form
a solid state bond having high reliability in the connection
between the components at low temperature and low load. At the same
time, in the solid state bonding, the metal material for bonding
does not flow out of the electrode areas, or the amount is very
small even if the metal material flows out. Therefore, it is
possible to effectively prevent the occurrence of a short between
the adjacent electrodes, compared with the connection by reflow.
Hence, it is possible to improve the yield of minute/narrow pitch
connections of the semiconductor devices. In addition, labor-hours
can be reduced since a leveling process such as CMP before
connecting is not required.
Other objects, features and advantages of the present invention
will become more apparent from the following detailed description
when read in conjunction with the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a side view showing an electronic component before an
activation process and for explaining an electrode connection
method according to a first embodiment of the present
invention;
FIG. 1B is a side view showing a circuit board before the
activation process and for explaining the electrode connection
method according to the first embodiment of the present
invention;
FIG. 2 is a block diagram for explaining an electrode surface
activation apparatus and an electrode connecting apparatus
according to a second embodiment of the present invention;
FIG. 3A is a side view showing the electronic component in a state
where the activation process is performed on electrodes and for
explaining the electrode connecting method according to the first
embodiment of the present invention;
FIG. 3B is a side view showing the circuit board in a state where
the activation process is performed on electrodes and for
explaining the electrode connecting method according to the first
embodiment of the present invention;
FIG. 4A is a side view showing the electronic component when an
adhesive film is applied to the electrodes and for explaining the
electrode connection method according to the first embodiment of
the present invention;
FIG. 4B is a side view showing the circuit board when an adhesive
film is applied to the electrodes and for explaining the electrode
connection method according to the first embodiment of the present
invention;
FIG. 5A is a side view showing the electronic component in a state
where the activated electrodes are coated with the adhesive film
and for explaining the electrode connection method according to the
first embodiment of the present invention;
FIG. 5B is a side view showing the circuit board in a state where
the activated electrodes are coated with the adhesive film and for
explaining the electrode connection method according to the first
embodiment of the present invention;
FIG. 6 is a side view showing the electronic component and the
circuit board located such that the respective electrodes face each
other and for explaining the electrode connection method according
to the first embodiment of the present invention;
FIG. 7 is a side view showing a state where the electrodes of the
electronic component and the electrodes of the circuit board are
heated and force is applied, and for explaining the electrode
connection method according to the first embodiment of the present
invention;
FIG. 8 is a side view showing a state where the electrodes of the
electronic component and the electrodes of the circuit board are
connected and for explaining the electrode connection method
according to the first embodiment of the present invention;
FIG. 9A is a side view of the electronic component 10 for
explaining a third embodiment of the present invention;
FIG. 9B is a side view of the circuit board 20 for explaining the
third embodiment of the present invention;
FIG. 10 is a side view of the electronic component 10 to which
electrodes Sn--Ag solder is applied;
FIG. 11A is a side view of the electronic component 10 put in a
chamber and irradiated with argon plasma;
FIG. 11B is a side view of the circuit board 20 put in the chamber
and irradiated with argon plasma;
FIG. 12 is a side view showing the electronic component 10 and the
circuit board 20 that are positioned and stacked such that the
respective electrodes face and contact each other via a solder
layers; and
FIG. 13 is a side view of a connected structure according to the
third embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A description will be given of embodiments of the present
invention, with reference to the drawings.
FIGS. 1A, 1B, and 3A through 8 are process drawings for explaining
an electrode connection method according to a first embodiment of
the present invention. FIG. 2 is a schematic block diagram of an
electrode surface activation apparatus and an electrode connection
apparatus according to a second embodiment of the present
invention.
In the following, a description will be given of an example where
component-side electrodes 12 formed on an electronic component 10
and board-side electrode 22 formed on a circuit board 20 are
connected. However, the present invention is not limited to the
connection of the electronic component 10 and the circuit board 20,
but can be widely applied to the connection of electrodes.
FIGS. 1A and 1B show the electronic component 10 and the circuit
board 20, respectively, before starting an electrode connection
process. The electronic component 10 is a semiconductor chip, for
example, and a plurality of component-side electrodes 12 are formed
thereon.
Additionally, the circuit board 20 is a board on which the
electronic component 10 is to be mounted. The circuit board 20 is a
flexible board, for example. The board-side electrodes 22
corresponding to the electronic component 10 are formed in the
predetermined location where the electronic component 10 is to be
mounted.
The component-side electrodes 12 formed on the electronic component
10 and the board-side electrodes 22 formed on the circuit board 20
are each protruding electrodes formed by electroless plating, for
instance. Accordingly, the electrodes 12 and 22 are each protruding
from the electrode forming surface of the electronic component 10
and the electrode forming surface of the circuit board 20,
respectively.
A description will be given of an electrode connection apparatus 40
used for connecting the electronic component 10 and circuit board
20 having the above-described structure.
FIG. 2 is a schematic block diagram of the electrode connection
apparatus 40. The electrode connection apparatus 40 generally
includes an electrode surface activation apparatus 41 and a
connecting apparatus 42. Further, the electrode surface activation
apparatus 41 generally includes an activation apparatus 44, a
coating apparatus 45, a film loader 46 and the like.
The activation apparatus 44 is the apparatus eliminating an oxide
from and activating component-side bonding surfaces 12a and
board-side bonding surfaces 22a that are surfaces of the
component-side electrodes 12 and the board-side electrodes 22,
respectively. In this embodiment, a plasma etching apparatus is
used in the activation apparatus 44.
The coating apparatus 45 is the apparatus for coating, with an
adhesive film 30, the component-side electrodes 12 and board-side
electrodes 22 that are activated by the activation apparatus 44.
Thus, the coating apparatus 45 is connected to the film loader 46
for supplying the adhesive film 30 to the coating apparatus 45. The
adhesive film 30 is carried to the coating apparatus 45 by the
carrying apparatus 47C.
On the other hand, the connecting apparatus 42 performs solid state
bonding on the component-side bonding surfaces 12a of the
component-side electrodes 12 and the board-side bonding surfaces
22a of the board-side electrode 22 that are activated. In this
embodiment, a flip chip bonder is used as the connecting apparatus
42.
A loader 43 contains the electronic component 10 and the circuit
board 20 in the state shown in FIGS. 1A and 1B, respectively. The
electronic component 10 and the circuit board 20 are carried to the
activation apparatus 44 at predetermined timings. In addition, an
unloader 48 contains the electronic component 10 and the circuit
board 20 that are integrated by the solid state bonding of
component-side electrodes 12 and the board-side electrodes 22.
Further, carrying apparatuses 47A through 47E carry the electronic
component 10 and the circuit board 20, or the adhesive film 30
among the apparatuses 42 through 48.
Next, referring to FIGS. 3A through 8, a detailed description will
be given of the connection process of the electronic component 10
and the circuit board 20 performed by using the electrode
connection apparatus 40 shown in FIG. 2.
The electronic component 10 and the circuit board 20 shown in FIGS.
1A and 1B, respectively, are contained in the loader 43 of the
electrode connection apparatus 40. The carrying apparatus 47A
carries the electronic component 10 and the circuit board 20 to the
activation apparatus 44 of the electrode surface activation
apparatus 41 at the predetermined intervals.
The activation apparatus 44 is a plasma etching apparatus. The
electronic component 10 and the circuit board 20 are carried to a
chamber of the activation apparatus 44 maintaining an atmosphere in
which argon plasma can be irradiated. Then, in the activation
apparatus 44, an etching process is performed such that the argon
plasma is irradiated to the component-side bonding surfaces 12a of
the component-side electrodes 12 and to the board-side bonding
surfaces 22a of the board-side electrodes 22. FIGS. 3A and 3B show
states where the argon plasma is irradiated to the component-side
bonding surfaces 12a and the board-side bonding surfaces 22a,
respectively.
By performing the plasma etching process in this manner, the
contamination such as the oxide film, moisture, and fats and oils
existing on the surfaces of each of the electrodes 12 and 22 is
eliminated, and the bonding surfaces 12a and 22a of the electrodes
12 and 22, respectively, are activated. Additionally, by activating
the component-side bonding surfaces 12a and the board-side bonding
surfaces 22a employing the plasma etching as in this embodiment, it
is possible to positively activate the bonding surfaces 12a and 22a
of the plurality of electrodes 12 and 22, respectively, at a high
throughput.
Further, the method of eliminating the oxide on each of the bonding
surfaces 12a and 22a so as to perform the activation is not limited
to the above-described plasma etching process. For example, it is
possible to activate the bonding surfaces 12a and 22a of the
electrodes 12 and 22, respectively, by spraying the steam of heated
carboxylic acid (formic acid of 250.degree. C., for example) on the
surfaces of each of the electrodes 12 and 22 so as to eliminate the
contamination by the reduction of the carboxylic acid. In a case
where such an activation method is employed, the equipment cost can
be reduced compared with the plasma etching.
When the activation process ends, the activation apparatus 44 is
purged with an inert gas so as to maintain the activated state of
each of the bonding surfaces 12a and 22a of the electronic
component 10 and the circuit board 20, respectively. Then, the
electronic component 10 and the circuit board 20 are carried to the
coating apparatus 45 by using the carrying apparatus 47B of which
carrying line is in the inert gas atmosphere.
The inside of the coating apparatus 45 is also in the inert gas.
Thus, during the carrying process from the activation process 44 to
the coating apparatus 45, the activated state of each of the
bonding surfaces 12a and 22a is not degraded. Further, the
atmospheres of the activation apparatus 44, the coating apparatus
45 and the carrying apparatus 47B are not limited to the inert gas
atmosphere. However, another atmosphere (vacuum atmosphere, for
example) may be set as long as the activated state of each of the
bonding surfaces 12a and 22 is maintained.
As mentioned above, the film loader 46 is connected to the coating
apparatus 45. The film loader 46 is constructed so as to supply
adhesive films 30A and 30B to the coating apparatus 45.
The film loader 46 performs a process of coating the activated
component-side electrodes 12 with the adhesive film 30A transferred
from the film loader 44 and a process of coating the activated
board-side electrodes 22 with the adhesive film 30B. It should be
noted that the adhesive film 30 is the general term for the
adhesive films 30A and 30B.
More specifically, as shown in FIGS. 4A and 4B, the adhesive films
30A and 30B supplied from the film loader 46 are arranged above the
electrode forming surfaces of the electronic component 10 and the
circuit board 20, respectively. Subsequently, pressure is applied
on the adhesive films 30A and 30B by a pressure board (not shown)
toward the electronic component 10 and the circuit board 20,
respectively. Thereafter, the pressure applied inside the coating
apparatus 45 is decreased.
Hence, as shown in FIGS. 5A and 5B, the electrodes 12 and 22 formed
on the electronic component 10 and the circuit board 20 are coated
by the adhesive films 30A and 30B, respectively. During the coating
process, by performing the coating with pressure and heat, it is
possible for the adhesive films 30A and 30B to positively adhere to
the electrodes 12 and 22, respectively. The adhesive films 30A and
30B are film resins. For the film resins, a thermosetting resin, a
thermoplastic resin, or a mixture of a thermosetting resin and a
thermoplastic resin may be used. For example, the thermosetting
resin may be epoxy resin such as bisphenol-A epoxy resin,
dicyclopentadien type epoxy resin, cresol novolak epoxy resin,
biphenyl epoxy resin and naphthalene type epoxy resin, or phenolic
resin such as resol type phenolic resin and novolak phenolic resin.
In addition, the thermoplastic resin may be, for example,
polyimide, polyamide, polyamide-imide, acrylic resin, polyester
resin, ABS resin, polycarbonate resin, phenoxy resin or the
like.
As described above, it is possible to maintain the sealing effect
even when the electronic component 10 and the circuit board 20 are
taken out from the electrode surface activation apparatus 41 and
placed in the air, by coating the activated component-side
electrodes 12 and board-side electrodes 22 (component-side bonding
surfaces 12a and board-side bonding surfaces 22a) with the adhesive
films 30A and 30B, respectively. Therefore, the activated state of
each of the bonding surfaces 12a and 22a is maintained by the
adhesive films 30A and 30B, respectively.
In addition, since the inside of the coating apparatus 45 is in the
inert gas atmosphere as mentioned above, there is no air causing
oxidation of the electrodes between the electrodes 12 and 22 and
the adhesive films 30A and 30B, respectively. Accordingly, it is
possible to securely maintain the activated state of the electrodes
12 and 22. Further, the activated state of the bonding surfaces 12a
and 22a are maintained by using the adhesive films 30A and 30B.
Thus, the process becomes easier compared with other coating
processes (for example, coating, plating, sputtering and so on).
Accordingly, it is possible to correspond to the automation of the
coating process of each of the electrodes 12 and 22 easily.
In addition, when there is a relatively long time until solid state
bonding (that will be described later) is performed after the
electrodes 12 and 22 are sealed with the adhesive films 30A and
30B, respectively, it is preferable that the electronic component
10 and the circuit board 20 coated with the adhesive films 30A and
30B, respectively, be maintained in an environment excluding the
air by placing the electronic component 10 and the circuit board 20
in a vacuum desiccator or the like, for example.
The connecting apparatus 42 is the flip chip bonder as described
above. The connecting apparatus 42 performs the bonding process of
the electronic component 10 and the circuit board 20. The flip chip
bonder forming the connecting apparatus 42 is generally used in the
semiconductor manufacturing processes and the like.
Consequently, unlike the activation apparatus 44 and the coating
apparatus 45, the connecting apparatus 42 is not provided with a
mechanism for setting the inert gas atmosphere or the vacuum
atmosphere. Accordingly, the equipment cost of connecting the
electronic component 10 and the circuit board 20 is reduced. At the
same time, the throughput of the connection process is improved,
and thus it is possible to correspond to the mass production
process.
When the electronic component 10 and the circuit board 20 are
carried inside the connecting apparatus 42, as shown in FIG. 6, the
electronic component 10 coated with the adhesive film 30A and the
circuit board 20 coated with the adhesive film 30B are located such
that the component-side electrodes 12 and the board-side electrodes
22 face each other. Subsequently, as shown in FIG. 7, the
electronic component 10 and the circuit board 20 are welded
together with pressure and heat. The pressure welding is performed
while correcting the shapes of the electronic component 10 and the
circuit board 20 so that warping is not caused.
Hence, the solid state bond between the component-side electrodes
12 and the board-side electrodes 22 is formed by breaking through
the adhesive films 30A and 30B. At this moment, the adhesive films
30A and 30B are cured without entering between the electrodes 12
and 22. Thus, it is possible to form the solid state bond having a
low interconnection resistance.
Additionally, as shown in FIG. 8, in a state where the
component-side electrodes 12 and the board-side electrodes 22 are
connected, the adhesive film 30 lies between the electronic
component 10 and the circuit board 20. Thus, the adhesive film 30
functions as an under fill resin. Accordingly, it is possible to
reinforce the bonding of the component-side electrodes 12 and the
board-side electrodes 22.
Further, as mentioned above, in this embodiment, since respective
electrodes 12 and 22 are formed by protruding electrodes (bumps),
it is possible to surely perform the process of breaking through
the adhesive films 30A and 30B in the solid state bonding.
Accordingly, it is possible to positively prevent the adhesive
films 30A and 30B from remaining in between the component-side
electrodes 12 and the board-side electrodes 22. Thus, the solid
state bonding of both electrodes 12 and 22 can be surely
formed.
Next, a description will be given of a third embodiment of the
present invention. It should be noted that, in a connection method
of electronic components according to the present invention,
components to be connected are connected by employing the flip chip
bonding method, and at least one of the components is an electronic
component such as a semiconductor chip and both components have
electrodes. The other one of the components may be a board for
mounting the electronic component, or another electronic
component.
The electrode surfaces of at least one of the components to be
connected are coated with a metal material having a Young's modulus
equal to or less than 50 GPa. As examples of the metal material
having Young's modulus equal to or less than 50 GPa, there are
various solder materials such as Sn and Sn alloy (for example,
Sn--Ag, Sn--Bi, Sn--Ag--Cu, Sn--In, and Sn--Pb alloy). These metals
or alloy materials easily form a solid solution with materials
generally used for the electrodes of the electronic components and
can form a strong bond. Thus, the metals and alloy materials are
suitable for the connection between the components to be connected
by the solid state bonding according to the present invention.
It is important for the metal material coating the electrode
surfaces to have a Young's modulus equal to or less than 50 GPa.
Such a metal material having a comparatively low Young's modulus is
easily leveled through plastic deformation when the load is applied
for forming a solid state bond between the components. Hence, it is
possible to form a firm solid state bond between the components
without performing a complex planarizing process by such as
CMP.
Generally, it is impossible to firmly bond the electrodes having
irregularities of the order of submicrons or microns on their
surfaces, unless the amount of the metal material on the electrodes
is small (adequate) and the metal material forms a layer of an
appropriate thickness. On the other hand, it is not preferable to
increase the amount of the metal material on the electrodes more
than necessary. The reason is that the metal material may flow out
of the electrode area by plastic deformation due to the load in
forming the solid state bond and cause a short between adjacent
electrodes especially in a case where the electrodes are formed
with narrow pitches. In general, when the metal material is applied
to the electrodes in an amount that forms a layer of 5 .mu.m
thickness, the plastically deformed metal material is sufficiently
supplied to the concave portions on the electrode surfaces having
the irregularities of the order of submicrons and microns. Thus,
the solution using the material of the electrodes and the metal
material is sufficient. Accordingly, it is possible to form the
solid state bond with high reliability without causing a short
between adjacent electrodes even when the electrodes are formed
with minute pitches. Therefore, generally, it is sufficient to set
approximately 5 .mu.m for the upper limit of the thickness of the
metal material applied to the electrodes. Of course, there may be a
case where it is necessary to more thickly apply the metal
material, according to the condition of the irregularity on the
electrode surfaces.
Arbitrary methods may be employed to coat the electrodes of the
components with the metal material, as long as the components are
not harmfully affected. As examples of such methods, there are the
dipping method of dipping the components in the melted metal
material, the ultrasonic soldering method of dipping the components
in the melted metal material under the application of ultrasonic
waves, the transfer (print) method, and the like.
Normally, an oxide film is formed on the electrode surfaces to
which the metal material is applied. In the connection by the solid
state bonding, it is possible to form a firm solid state bond such
that the metal material of the electrodes and the metal adhering to
the electrode surfaces directly contact each other. Consequently,
in order to achieve the firmer connection between the components by
the solid state bonding, it is preferable to apply the metal
material to the electrode surfaces after eliminating the oxide film
thereon. For example, when the sputtering method is employed, it is
possible to apply the metal material to the electrodes while
eliminating the oxide film. In addition, the oxide films on the
electrode surfaces can be eliminated by irradiating (treatment by
plasma) with an inert ion beam or a neutral atom beam.
Following the application of the metal material for bonding to the
electrode surfaces, activation is performed on the surface of the
metal material applied to the electrodes and the electrode surfaces
of the component when there is a component to which electrode
surfaces the metal material is not applied. The activation is the
process of exposing the metal material itself of the electrodes and
the metal material for bonding itself to the surface by eliminating
the oxide films formed on the surface of the metal material applied
to the electrodes as well as the electrode surfaces to which the
metal material is not applied. The process can be performed by
irradiating (a plasma treatment) an inert ion beam or a neutral
atom beam, for example. According to the process, it is possible to
eliminate contamination such as moisture and fats and oils as well
as the oxide film on the surface of the metal material. The
elimination of the oxide film may be performed by the reduction of
an oxide in a heated carboxylic acid atmosphere, for example, in
the vapor of formic acid of 250.degree. C. The specific methods of
the activation process are not limited to the above-described
methods. Any methods may be employed as long as the methods do not
have harmful effect on the components to be connected.
The components after the activation process of the surface of the
metal material are positioned and superposed on each other such
that the respective electrodes face each other and make contact via
the metal material for bonding. Then, the components are pressed to
form a solid state bond. Thus, it is possible to bond the
components firmly at room temperature. The solid state bond may be
formed under the condition that the temperature is raised equal to
or less than the melting point of the metal material for bonding
applied to the electrodes. However, such heating is not always
necessary. The suitable load in pressing may be selected according
to the kinds of the components or the kind of the metal material
for bonding.
The two components that are connected as mentioned above form a
connected structure in which both electrodes are firmly connected
via the metal material for bonding between the electrodes.
A description will be given of a third embodiment of the present
invention.
First, as shown in FIGS. 9A and 9B, the protruding electrodes 12
and 22 are formed on the electrode forming parts of the
semiconductor chip (electronic component) 10 and that of the
circuit board 20, respectively, by a common electroless plating
method.
Next, as shown in FIG. 10, Sn--Ag solder is applied on the
protruding electrodes 12 of the semiconductor chip 10 by ultrasonic
soldering. Sn--Ag solder layers 50 of approximately 5 .mu.m
thickness are formed on the electrodes 12 such that the solder bath
equipped with an ultrasonic transducer having output power of 40W
and frequency of 20 kHz is used, the temperature of the solder bath
is set to 280.degree. C. while a nitrogen gas flows at 60 L/min,
and the semiconductor chip 10 is dipped into the solder bath for
0.5 to 2 seconds, taken out from the solder bath and the solder is
solidified.
Then, as shown in FIGS. 11A and 11B, the semiconductor chip 10 and
the circuit board 20 are put in a chamber (not shown) maintaining
an atmosphere where argon plasma 31 can be irradiated. Then the
argon plasma 31 is irradiated so as to etch the surfaces of the
solder layers 50 formed on the electrodes 12 of the semiconductor
chip 10 and the surfaces of the electrodes 22 of the circuit board
20. Hence, the oxide films on the surfaces of the solder layers 50
and the electrodes 22 are eliminated together with moisture and
fats and oils. Thus, the respective surfaces of the solder layers
50 and the electrodes 22 are activated.
Subsequently, the chamber is maintained to have a vacuum atmosphere
inside (or an atmosphere where oxygen does not exist such as an
inert gas atmosphere). As shown in FIG. 12, the semiconductor chip
10 and the circuit board 20 are positioned and stacked such that
the respective electrodes 12 and 22 face and contact each other via
the solder layers 50. Then, the semiconductor chip 10 and the
circuit board 20 are pressed by 5 through 10 N/mm.sup.2 at room
temperature so as to form a solid state bond. Hence, a connected
structure 1 of the semiconductor chip 10 and the circuit board 20
as shown in FIG. 13 is obtained. In the connected structure 1, the
semiconductor chip 10 and the circuit board 20 are firmly connected
via the respective electrodes 12 and 22 and the Sn--Ag solder
layers 50 therebetween.
In the third embodiment, the solder layers 50 are formed on the
electrodes 12 of the semiconductor chip 10. However, such solder
layers may be formed on the electrodes 22 of the circuit board 20,
or on both electrodes 12 and 22.
The present invention is not limited to the specifically disclosed
embodiments, and variations and modifications may be made without
departing from the scope of the present invention.
* * * * *